1. Field of the Invention
This invention relates to an image processing device which performs processing of output image data on a page basis or on a document basis.
2. Description of the Related Art
Conventionally, there is proposed an image processing method in which additional information indicating that image data of concern is secret data is extracted from the image data of concern and the copying of the image data is inhibited according to the extracted additional information. As application of the above method, there is also proposed an image processing method which performs processing of image data in accordance with the extracted additional information. Generally, the additional information added to image data may be used in digital watermarking or may be used as a ground tint added to image data.
Japanese Laid-Open Patent Application No. 2004-200962 discloses an image processing method in which, when copying a series of document images, the dot pattern added to each document image is detected, and the processing to be performed for the series of document images as a whole is determined. According to this method, even when a secret data is contained only in a part of the series of document images which are to be copied, the copying of the series of document images as a whole is inhibited. This method is intended to prevent leaking of confidential information certainly.
However, in the method of Japanese Laid-Open Patent Application No. 2004-200962, the outputting of all the document images is inhibited, and there is a problem that this method lacks the user friendliness. For example, even when the user desires to copy the other document images different from a document image containing secret data, the copying of the other document images is impossible according to the method of Japanese Laid-Open Patent Application No. 2004-200962.
Moreover, if a series of document images except for a document image-containing secret data are copied, the person who receives the copied documents may recognize accidentally that the original document images do not contain any secret data. Therefore, there is also a possibility that the credibility of the original documents may fall.